Rear-projection screen

Abstract

A transparent, rear-light projection screen that has lenses on its back side facing the projectors for paralleling light from the projectors. The screen on its front side has upright, forerunning asymmetric cylinder lenses with partially reflecting projections having light-refractive surfaces, facing outwardly from the front side and opposite to the direction from which the paralleled light originates from behind. The projection screen improves the color contrast and increases the projected light when the screen is viewed from a side direction.

We claim: 
     
       1. A transparent rear-projection screen having a rear side comprising lenses for paralleling light coming from behind the screen, and having a front side comprising rectilinear, convex lenses wherein at essentially a mid-point of a plurality of adjacent convex lenses, projections are provided each of which projections has opposite side surfaces provided with light diffusing means for diffusing light incident thereto. 
     
     
       2. A screen according to claim 1, wherein the projections are in the form of lenses having essentially a triangular cross-section and the projections are connected by asymmetric, convex lenses. 
     
     
       3. A screen according to claim 1, wherein an angle between a tangent of the convex lenses and a radius of said convex lens is 80° at a point at which the projections are connected to the convex lenses. 
     
     
       4. A screen according to claim 1, wherein the light diffusing means is produced by a lacquer-coating mixed with wax and CaCO 3 , where said wax and CaCO 3  have an index of refraction of from 0.02 to 0.06. 
     
     
       5. A screen according to claim 1, comprising a light refracting medium containing an organic or inorganic pigment evenly distributed in a cross-section of the entire medium, or in one of the sides of the screen. 
     
     
       6. A screen according to claim 1, wherein the rear side of the screen comprises lenses for diffusion of the light vertically. 
     
     
       7. A transparent rear-projection screen having a rear side and a front side, wherein said rear side comprises lenses for paralleling light received by the rear side of the screen, and the front side comprises rectilinear, convex lenses having projections at about a mid-point of adjacent convex lenses, each of the projections having opposite side surfaces provided with light diffusing means for diffusing light incident thereto. 
     
     
       8. A screen according to claim 7, wherein the lenses on the rear side comprise Fresnel lens. 
     
     
       9. A screen according to claim 8, wherein the light diffusing means is a coating for deflecting light striking said sides from within said mid-point projections and diffusing the light passing through the sides of said mid-point projections. 
     
     
       10. A screen according to claim 9, wherein said coating comprises a thickness of from 1 to 3 microns. 
     
     
       11. A screen according to claim 9, wherein said coating comprises a layer of lacquer having a refractive index equal to or greater than a refractive index of a basic material of said screen. 
     
     
       12. A screen according to claim 9, wherein said coating has a predetermined amount of wax added to the lacquer to achieve a desired diffusion of light from the sides of the projections within a predetermined area of deflection. 
     
     
       13. A screen according to claim 9, wherein the sides of projections are planar and form a predetermined angle with one another. 
     
     
       14. A screen according to claim 9, wherein the sides of the projections have a non-planar, wavey surface that form a predetermined angle with one another. 
     
     
       15. A transparent rear-projection screen having a rear side comprising lenses for paralleling light coming from behind the screen, and having a front side comprising a plurality of convex lenses positioned one next to the other in a rectilinear manner, each convex lens comprising: (a) a first convex lens surface having a low end attached to an adjacent convex lens, and a high end attached to a base of a mid-point lens projection, and   (b) a second convex lens surface having a low end attached to an adjacent convex lens and a high end attached to a base of a mid projection lens, and   (c) a mid-lens projection having a base attached to the high side of said first convex lens and the high side of said second convex lens, wherein said first convex lens and said second convex lens are symmetrical with respect to said mid-lens projection.   
     
     
       16. A screen according to claim 15, wherein said mid-lens projection has substantially a triangular cross-section pointing outwardly from the front side of the screen with sides that are partially reflecting and have a light-refracting surface, where an extension of said sides forms a predetermined angle β. 
     
     
       17. A screen according to claim 16, wherein said first convex lens surface and said second convex lens surface each have a predetermined radius of curvature R, said mid-lens projection has a predetermined base width W, and said convex lens has a predetermined diameter D, and said sides of said mid-lens projection form an angle β with one another. 
     
     
       18. A screen according to claim 17, wherein a tangent to a point where the first convex lens makes contact with the base of mid-lens projection forms an angle γ with a normal to a surface of the screen front side, and wherein elements of the screen have substantially the following dimensions: Gamma=80°   Beta=40°   W=0.14 mm   D=0.40 mm   R=0.15 mm.   
     
     
       19. A screen according to claim 16, wherein said sides have a coating comprising a lacquer having an index of refraction of approximately 1.50 to which has been added predetermined amounts of wax and CaCO 3 . 
     
     
       20. A screen according to claim 15, wherein the rear projection screen is made of a basic material containing a diffusing medium, said diffusing medium comprising a fine-powdered glass or one of the compounds from the group of SiO 2 , CaCO 3  or BaSO 4 , said diffusing medium having an index of refraction of from 0.05 to 0.07 larger or smaller than an index of refraction of the basic material of the screen. 
     
     
       21. A screen according to claim 20, wherein said basic material is acrylic.